G5 wake from sleep, configd, cups?

I have a nagging problem with my G5 (1.8 GHz single, 512 MB). Sometimes, it won't wake up from sleep. That is: iTunes plays (via a script), the eject key works but the display stays dark. After calling Apple a number of times to no avail (reset PRM, reset SMU) I finally found a mention of this problem on an Apple forum:

Since I set my G5 to "never sleep", I am able to log in via SSH and poke around when it refuses to wake up, which happened this morning again. Indeed, ps -aux shows configd in the "Us" state, but is very hard to kill.
kill (pid) does not work
kill -1 (pid) shuts down my SSH conection and after that, I can't reach the G5 anymore by SSH.